1. Field of the Invention
The present invention relates to a non-volatile memory device, and more particularly, to a non-volatile memory device which has improved electrical characteristics, and a method of fabricating the non-volatile memory device.
2. Description of the Related Art
Floating gate-type non-volatile memory devices are widely used in various industrial fields. In response to a strong demand for miniaturized floating gate-type non-volatile memory devices, non-volatile memory devices having a high integration density have been rapidly developed. However, there is a clear limit in the extent to which floating gate-type non-volatile memory devices can be miniaturized because a high voltage is always required for programming or erasure, and if the floating gate-type non-volatile memory device is excessively miniaturized, it may be difficult or even impossible to secure sufficient margins during the manufacture of the floating gate-type non-volatile memory device.
Therefore, research has been vigorously carried out on various alternatives to the floating gate-type non-volatile memory device. In particular, polysilicon-oxide-nitride-tunnel-thin oxide-semiconductor (SONOS) non-volatile memory devices have drawn much interest as a next generation device that will replace the floating gate-type non-volatile memory device.
Recently, a stack-type SONOS non-volatile memory device in which a thin oxide layer, which serves as a tunneling layer, a silicon nitride layer, which serves as a charge trapping layer, and an oxide layer, which serves as an electron shield layer, are sequentially stacked, has been widely used. More recently, a local type SONOS non-volatile memory device in which an ONO structure is formed to be only a part of a gate has been developed.
While the local type SONOS non-volatile memory device can be efficiently programmed and erased, it is difficult to control the length of the ONO structure because, the ONO structure is formed and then the gate is formed. In addition, if the local type SONOS non-volatile memory device is miniaturized, the characteristics of the local type SONOS non-volatile memory device may degrade due to variation in the length of the ONO structure.